I've been turning it over in my head a bit recently, and I cannot come up with a good reason why there should not be threaded comments on questions. I do not think threaded comments would be beneficial on answers, as they would encourage multiple discussions in the answer comments.

Can anyone think of a good reason that questions shouldn't have threaded comments?

My concern is cases where the information in the question is lacking and multiple people begin asking for different types of clarification, which is all too common here. My thinking was that it would be easier, and thus quicker, if these could be threaded, even one deep, possibly using the @ syntax to group them.
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mor7iferApr 15 '12 at 18:00

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@m0r7if3r as above - if question is so bad or unclear that it requires so much discussion it would be more appropriate just to close it and advise asker to rework it. It is not in site's best interest that time and typing are spent in trying to salvage poor questions.
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Rarst♦Apr 15 '12 at 18:16

I think its a good idea as it would allow the opportunity to respond directly to comments which could in fact be beneficial to the quality of the thread, overall improving the answer.

It's a question of how deep do you nest the comments though? Too deep and it gets hard to follow as the width of the available comment area decreases. How this reflects upon additional code and other formatting would be my concern.

I'd be happy to see either the ability to nest comments one level deep within a parent-comment item or alternatively and possibly an even better solution would be to provide a REPLY TO -> button, much like that found in the chat rooms which means you could in theory then extend a threaded-like reply to system onto the answers as well as the question itself.

Essentially we would leave the current comment format the same, but possibly provide an additional view/toggle which you can switch between to see relationships between comments.

If we thought about there's probably a number of ways we could group related comments together that are not intrusive to the formatting of the site as it currently stands.